The present invention relates to an apparatus for driving a medical appliance such as an artificial heart or balloon pump in an artery, and more particularly, to a fluid driving apparatus for changing a positive and negative fluid pressure.
A conventional driving apparatus for a medical appliance is shown in, for example, Japanese Kokai Application No. 61(1986)-129500. In this conventional apparatus, the inlet terminal of the compressor is used for a negative pressure source and the outlet terminal of the compressor is used for a positive pressure source. Thus, this apparatus does not have a separate vacuum pump for negative pressure. This apparatus also has a valve 18 which connects the outlet terminal of the compressor to the atmosphere and a valve 19 which connects the inlet terminal of the compressor to the atmosphere. This apparatus controls valves 18 and 19 as follows:
1) positive pressure mode if, PA1 2) negative pressure mode if,
a) pressure of the positive accumulator&lt;Ps1: 18 close, 19 open PA2 b) pressure of the negative accumulator&gt;Vs2: 18 open, 19 close PA2 c) not a) or b):18 open, 19 open PA2 d) pressure of the negative accumulator.gtoreq.Vs1:18 open, 19 close PA2 e) pressure of the positive accumulator Ps2:18 close, 19 open PA2 f) not d) or e):18 open, 19 open
wherein, Ps1, Ps2, Vs1 and Vs2 are set values.
In this apparatus, when it is in a positive pressure mode, positive pressure regulation has priority and when it is in a negative pressure mode, negative pressure regulation has priority. The set values are different in each mode.
However, this apparatus has a loss of generated pressure because the compressor has to be operated often in the idle mode which is the above mentioned cases c) and f). This makes the compressor big in size. In addition to this loss in this apparatus, the priority of the pressure regulations is changed in response to the pressure changes between positive and negative so that the valve 18 or valve 19 connects the compressor to the atmosphere. Because the compressor is connected to the positive and negative pressure accumulators by relatively large diameter pipes, when the valve 18 or valve 19 is opened, the pressures in the pipes are exhausted to the atmosphere. This makes for a loss of generated pressures which are increased when the changing frequency of positive and negative pressures is increased. Furthermore, this apparatus makes undesirable noise because of these drawbacks.